Before approaching a bulbdog, Make sure you have aquatic mushrooms. The amount varies between levels. All you have to do it out the mushroom into your inventory slot and approach the animal. Press Y ( On Xbox) to feed it. There should be a bar that shows its taming level. On a lystro if you walk to far from it, The taming restarts ( At least it did for me ) I am unsure if it is the same for bulbdogs. But better safe then sorry . . !!